IRPCS and why you have to get out the way

[DAKA]

john morris asked me to explain this here after we touched on the subject in the lounge.

This explanation is what Tim Bartlet, PaulGooch,Haydn and myself were discussing and for a change agreeing when the lumberjack thread got pulled.

I hope you can read it with an open mind, I'm not very good at putting my thoughts across so its up to you to interpret it into your situation.

In my opinion it fully explains why in the past Tim has frequently been unable to win his point of view across to experienced channel crossers.

It all about perception of distance and realistic horizons.

A ships captain is looking from the top of his tower.

A sailing boat skipper is looking from the bottom of his sail.

The ships captain sees the sail long before the sailing boat skipper sees the tanker.

Add to this the stable platform the ships captain has along with exceptional radar compared with the sailing boat skipper and you should begin to realize that all the forum members who say most ships alter for them could well be right but as the alteration happened before the ship came into view of the sailing boat the other half of the forum members believe that ships dont alter at all .

The ship can only realistically alter a few degrees so the alteration will be small and a long way off.

As you cant see the ship you may well unwittingly tack into the path of the ship and you cant expect the ship to keep altering for you as other event preclude this. There could well be other obstacles that you cant see to prevent him .

Seeing as by the time you see the ship he will have already taken the action he feels is appropriate then you have to decide if his action is adequate , monitor for a short duration and if you feel he is too close then it is time for you to take action to comply with your equal duty to avoid a collision and get out the way.



The lumberjack thread really was an important thread which carried a very important message and explained the differences between the desk commodores and the experienced channel crossers.

Tim's explanation was far easier to understand explaining with greater technical accuracy .
Now you have read it make your own mind up if you are going to stand on to a tanker/container ship @ 20knots .

perception of distance

You think a ship is a mile away when due to its sheer size it is two miles away.

Many forum members who say they dont stand on within two miles are most likely actually within a mile which is certainly time to get out the way, thats less than 3 minutes to impact !


You need to know IRPCS for your RYA exam.

You have the benefit of experienced channel crossers and how they act in reality .

Now you have the knowledge that brings the two practices safely together although its a shame Tim isnt here to put it across in a way that is easier to understand .

 

[jimi]

So to summarise for a stand on vessel:


1) Chances are you've been seen and action already has been taken by the giveway vessel to avoid you by the time you are aware of it if you are working by sight alone.
2) If you wish to take action take it as soon as poss and make it very substantial.


Is that a fair summary?

 

[Neil_Y]

I just need a "like" button, that about sums it up and I missed the pulled thread. Once on an empty ocean a fast container boat appeared, so I called him up to say hi and asked the question. He'd seen us 15 min or more before we'd seen him and had altered course to miss us. To us it looked close until the last 5 mins when he passed 200m ahead of us. We had a long chat about how bored you can get keeping a look out.

 

[fireball]

In these days of AIS we've probably clocked the ship before he's clocked us ..

Not sure about standing on to 2 or even 1 mile - I chicken out long before then - on the basis that at 6kts it takes 20 mins to do 2 miles I feel it best to take action then - because if I've cocked up and he's already altered course or there is something else in the way then I've still got time to clear.

 

[bedouin]

I must admit I'm a little confused.

Your post seems to be saying that the ship will probably already have altered course - so that seems to imply that you should stand on.

Without re-igniting the debate, could you clarify what you meant to say?

 

[wadget]

In these days of AIS we've probably clocked the ship before he's clocked us ..

Not sure about standing on to 2 or even 1 mile - I chicken out long before then - on the basis that at 6kts it takes 20 mins to do 2 miles I feel it best to take action then - because if I've cocked up and he's already altered course or there is something else in the way then I've still got time to clear.

Well it depends on what AIS equipment you both have. On a modern ship you will usually have the radar set up so that you can see 20 miles ahead so the ship can still probably see you before you see them or at least you will see each other at roughly the same time.

 

[oldbilbo]

That big ships' watchkeepers can often see you ( me ) at extended range is all very well, and often is probably the case, but numerous accident investigation reports make it plain as day that you ( me ) cannot rely on being seen early for our safe collision avoidance. That's 'copping out' of our responsibilities to the people with us - some of whom matter.

One example of many....

Some years ago meself was transiting south some 300nm west of Ushant, in a large catamaran flying a bright red/white/blue spinnaker, single watchkeeper, clear viz. and flat seas. around 0730hrs.

A Very Large Container Ship ( VLCS ) came hull-up heading east-ish, and repeated handbearings indicated a 'risk of collision' was developing. I considered my obligations and options, and called the VLCS at about 5-6 miles. After quite a few long seconds, a young and seemingly startled voice replied, asking what ship and where were we....

I responded with 'type and vector', repeating my request for her intentions. By this time it was clear that a close-quarters situation would result, and I had called the other crewmember, reluctant, from his sleep below and started engines. Then the ship replied - a much older voice - stating that they now saw us and would keep clear. The aspect started to change quite swiftly, and she passed about half a mile astern.

I thanked the VLCS with 'Linea Mexicana' painted in 30-foot letters on her side. We went on our respective ways. I still believe that the early morning sun and the container-handling derricks obscured the young watchkeeper's lookout. They wouldn't have felt even a bump....


Here's a pic of a model....

 

[sarabande]

to see (non radar) an approaching ship at twenty miles means that your combined height of eye has to be at least 290ft ASL.

and unless you have sneaky and very very expensive over-the-horizon radar.....

 

[Bru]

Thjs is how I read the collected, erm, wisdom ...

In an open water encounter between a sailing (or for that matter motor) yacht and a large commercial vessel ...

If you are the stand on vessel (and if you are under sail, all other things being equal, you will be) you should, under normal circumstances, stand on UNTIL it becomes clear that the other vessel has not taken adequate action to avoid a collision

You are not expected or required to stand on into danger

At what point you make that decision is a judgement call which cannot readily be broken down into fixed numbers but a range of 1 to 2 miles would certainly be minimal if the other vessel is moving at 15 to 20 knots

Once you make the decision to take avoiding action, the action you take should be very obvious and not a slight alteration and any turn should be to starboard if possible (turning to port is actively discouraged in the regs)

What you should not do is waffle around like a loose canon making several small alterations of course

In confined waters on a busy day with lots of leisure craft batting about, yacht and dingy races taking place, ferry movements and large ship movements, it may be reasonable to consider a large vessel to be constrained in its ability to maneouvre since an alteration of course by the large vessel to avoid one collision situation is very likely going to lead to another collision situation (this is perhaps the source of the notion that large vessels ignore colregs - in places like the Solent they may have little other option other than to continue on a clear course and let all the small fry like us bounce off them in effect)

The title of this thread is misleading (again) because you do NOT have to automatically get out of the way. If the maritime industry required yachts to "get out of the way" of big ships regardless of circumstances, the Regulations would stipulate it. They do not.

 

[A1Sailor]

In these days of AIS we've probably clocked the ship before he's clocked us ..

Not sure I follow this. It seems to be the complete opposite of the OP's summary.
Are you assuming that all yachts send and receive AIS? If so, you are mistaken.

 

[little_roundtop]

Not sure I follow this. It seems to be the complete opposite of the OP's summary.
Are you assuming that all yachts send and receive AIS? If so, you are mistaken.

That's true, but perhaps all ocean-going yachts should be required to receive AIS? It takes all the guesswork out of collision avoidance. With AIS, pretty soon after your AIS set has seen the big ship you know without doubt whether a risk of collision exists and how long you have before it happens.

IRPCS Rule 5 does say

Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and or the risk of collision

Perhaps, given it's fairly low cost, it's time to make AIS reception a mandatory requirement on all ocean-going yachts?

 

[John Barry]

to see (non radar) an approaching ship at twenty miles means that your combined height of eye has to be at least 290ft ASL.

Sorry, but I don't agree with your maths.

Firstly you shouldn't base it on combined height, you need to do two separate calculations. The formula for horizon distance is miles = 2.08 x sqrt(height in m).

For a yacht with a 3m eye height the horizon is 3.6 miles
A point on an approaching ship 62m above sea level will have a horizon of 16.4 miles. Total 20 miles. Combined height 65m = 65/.3048 = 213 colonial foots.

More to the point you are not likley to see anything at 20 miles no matter how high it is. Spotting anything further than 10 miles away needs exceptional visibility and a long time scanning the horizon.

 

[A1Sailor]

Perhaps, given it's fairly low cost, it's time to make AIS reception a mandatory requirement on all ocean-going yachts?

Perhaps - but most of us don't own ocean-going yachts. The issues are perhaps more relevant for coastal cruising than for crossing oceans. If I am duty bound to use "all available means" should I fit radar too?
A crows nest might be over the top...

 

[Blue5]

The beauty of AIS is that you can see them on the screen long before they are visible and from the ship details page you can see if any degree of rudder is applied to alter course.

On two occasions I have called a vessel when unsure of the situation and on both occasions following contact I have witnessed rudder being applied in the AIS detail page, this would suggest to me I had not been seen.

 

[prv]

If I am duty bound to use "all available means" should I fit radar too?

I believe the intention is "all means available on board at the time". After all, the duty is on the watchkeeper on the bridge, who (on ships) will have no choice about what equipment the owners decided to fit.

It does mean that if you have a working radar you must use it, though that's generally ignored on yachts in good weather.

Pete

 

[webcraft]

You need to know IRPCS for your RYA exam.

You have the benefit of experienced channel crossers and how they act in reality .

The Channel? Are you sure we aren't talking about

?

If you really believe that you only need to know the IRPCS to pass an exam then you are an even bigger menace than I have previously taken you for.

- W

 

[DAKA]

If you really believe that you only need to know the IRPCS to pass an exam then you are an even bigger menace than I have previously taken you for.

I really didnt want to post on scuttlebutts because I knew someone would turn it into a trolls playground and I should have known it would be you.

You are welcome to join in and learn but you have have to pay far better attention if you dont want to end up looking like an idiot or troll yourself.

You have deliberately only quoted two of the three pointers

a)You need to know IRPCS for your RYA exam.

b) You have the benefit of experienced channel crossers and how they act in reality .

c) Now you have the knowledge that brings the two practices safely together

I am attempting to encourage complete compliance with IRPCS , which includes standing on in compliance with IRPCS until you believe the ship is still on a course which is too close for your comfort.

We ALL agree on that , all always have done.

The argument is about when the duty to stand on expires.

The lumberjack thread helped me in understanding why such an apparent gap used to exist between myself and desk commodores.

Read it again webby and see if it helps you to understand why your post is so silly.


clue
Like a couple of kids arguing on a bridge over a marina ..........

dummy 1

" no the marina is on the left hand side of the river"

webby 2

" no it isnt you idiot, its on the right hand side of the river"


Then you realize that two intelligent and experienced boaters cant be both wrong , spot the obvious and you both look from the same side of the bridge and all is revealed ..............

 

[wadget]

Sorry, but I don't agree with your maths.

Firstly you shouldn't base it on combined height, you need to do two separate calculations. The formula for horizon distance is miles = 2.08 x sqrt(height in m).

For a yacht with a 3m eye height the horizon is 3.6 miles
A point on an approaching ship 62m above sea level will have a horizon of 16.4 miles. Total 20 miles. Combined height 65m = 65/.3048 = 213 colonial foots.

More to the point you are not likley to see anything at 20 miles no matter how high it is. Spotting anything further than 10 miles away needs exceptional visibility and a long time scanning the horizon.

Sorry my point was that on the bridge of a ship you will instantly see AIS targets at a range of around 20 miles on the radar screen. Obviously that is presuming that yachts are transmitting AIS data which in my opinion they should be. The AIS receivers are pointless just spend the extra money on a transmitter.

 

[Searush]

Perhaps - but most of us don't own ocean-going yachts. The issues are perhaps more relevant for coastal cruising than for crossing oceans. If I am duty bound to use "all available means" should I fit radar too?
A crows nest might be over the top...

If you don't have them fitted, all these fancy aids are not available to you, are they?


Duh! PRV beat me to it.

 

[John Barry]

Sorry my point was that on the bridge of a ship you will instantly see AIS targets at a range of around 20 miles on the radar screen. Obviously that is presuming that yachts are transmitting AIS data which in my opinion they should be. The AIS receivers are pointless just spend the extra money on a transmitter.

I think that that is a very unsafe presumption. Whilst you may have a point (others will argue, I'm sure) that yachts should have an AIS transmitter the fact is that very few do.
From the bridge of a ship the only way you'll see 95% of yachts is through radar or the mark one eyeball. With radar you may spot a yacht at 20 miles (I wouldn't bet on it). Using the mark one has no real chance.